Inflatable mattress with fluid amplifier



July 2, 1968 D. R. JONES 3,390,674

INFLATABLE MATTRESS WITH FLUID AMPLIFIER Filed May 28, 1965 INVENTORDONNIE ROLAND JONES ATTORNEYS United States Patent 3,390,674 INFLATABLEMATTRESS WITH FLUID AMPLIFIER Donnie Roland Jones, Silver Spring, Md.,assignor to Bowles Engineering Corporation, Silver Spring, Md., acorporation of Maryland Filed May 28, 1965, Ser. No. 459,705 7 Claims.(Cl. 128-33) ABSTRACT OF THE DISCLOSURE An inflatable mattress having afirst group of inflatable sections isolated from and interleaved with asecond group of inflatable sections, each group being connected to arespective fluid conduit. The conduits receive fluid flow from arespective pair of output passages of a pure fluid bistable element ofthe type which normally maintains its binary state irrespective ofoutput passage backloading. A feedback passage extends from each outputpassage to a respective control nozzle of said bistable element forproviding signals to change the binary state of the element whenevereach group of inflatable sections is inflated sufliciently to produce apredetermined back pressure in its associated output passage.

The present invention relates to inflatable mattresses and similar typesof body supports and, more particularly, to an inflatable mattress orbody support and a control therefor such that the areas of support ofthe body may be cyclically altered so that no area of high pressurebetween the body and the support is maintained for an in definite lengthof time thereby resulting in increased comfort for the user.

It was determined some years ago that one of the contributing factors tobed sores in bedridden and substantially immobile patients resulted fromsustained areas of high pressure contact between a mattress and the bodyof the individual. In order to overcome this difficulty, it wassuggested that a mattress be provided having a plurality of generallyparallel air passages with, for instance, the odd number of passagesconnected to a first manifold and the even number of passages connectedto a second manifold. Timing means were employed to connect the twomanifolds alternately and cyclically to a source of air pressure so thatadjoining segments or passages were alternately expanded and exhausted.Such an arrangement effected a cyclic shifting of the body supportareas, thus eliminating sustained high pressure contact between the bodyof the user and the support.

Such mattresses have been found to be quite satisfactory in preventingbed sores, but the dilficulty with such apparatus is the relatively highcost due to the large number of mechanical parts required in the controlmechanism to effect the desired cycling of air to the two manifolds. Inone typical such prior art device, the mechanical components required,in addition to a motor and pump, were two spool valves, one shuttlevalve, two check valves, one timer motor with cam and two cam followers.

In accordance with the present invention, all of the above mechanicalcomponents may be replaced by a single pure fluid flip-flop of suchconstruction that, in conjunction with the air mattress, the flip-flopoperates as an oscillator. The oscillator frequency dependson the nozzlesize and can be designed to cycle from a few seconds or less to severalminutes, limited only by the mechanical construction technique.

A pure fluid flip-flop is a fluid element having two stable states. Astream of fluid is issued by a power nozzle through an interactionregion towards two fluid receiving passages. In a typical such devicesidewalls, em-

Patented July 2, 1968 ice ploye'd to define the lateral sides of theinteraction region, are located such with respect to the power nozzlethat, when the stream is directed to one of the output passages, aboundary layer develops between the adjacent sidewall and the stream tomaintain the stream in its deflected position. An input flow of fluidmay be provided to switch the stream to the other output passages andagain, a boundary layer is developed between the power stream and theother sidewall to maintain the stream deflected to the second outputpassage.

Boundary layer fluid amplifiers may be made either sensitive orinsensitive to load on the output passages. More particularly, a devicemay be made such that, if the passage is heavily loaded, the stream,after an initial deflection to an output passage, is deflected to theother output passage due to backloading. Alternatively, the device maybe made insensitive to the load so that, once the stream is directed toan output passage, it remains directed to this passage regardless of theload. The present invention employs the latter type of boundary layerunit; that is, one which is insensitive to the load on the device.

Initially, it was attempted to employ a flip-flop sensitive tobackloading such that, when a stream is initially deflected to oneoutput passage and is conveyed by suitable means to one of the manifoldsof the mattress, the stream maintains its deflection to this outputpassage until all of the passages in the mattress associated with theaforesaid manifold are substantially completely inflated. At this time,the load on the output passage is greatly increased above that which ispresent when the stream is initially deflected to this first outputpassage. As a result of the increase in load, the flip-flop is caused toswitch to the other output passage and air is now supplied to the secondmanifold and through this manifold to the second plurality of passagesin the mattress. The second plurality of passages begins to inflate,while due to the loss of pressure in the manifold associated with thefirst plurality of passages in the mattress, these passages begin todeflate. The air from this first plurality of passages may be entrainedin the power stream and now transferred with the power stream to thesecond output passages and thence to the second plurality of passages inthe mattress. When the second plurality of passages in the mattressbecome fully inflated, the second output passage of the flip-flop issuiliciently backloaded to produce switching of the flipflop and thispower stream is now deflected to the first output passage and the cycleis repeated. It was found, however, that with this type of unit it wasdifficult to obtain full inflation of the mattress passages and at thesame time insure switching of the power stream.

It has been found that the above difliculties may be overcome byemploying a flip-flop insensitive to load changes and utilizing twofeedback passages to effect switching. More particularly, the flip-flopis provided with two control nozzles on opposite sides of the powerstream. Each of these control nozzles is connected through a passage toa point near the adjacent output channel of the flip-flop. When a streamis deflected to a particular output passage, its movement past the inletorifice to the feedback channel tends to extract fluid from this channeland the reduced pressure thereby produced is transmitted through thefeedback passage to the boundary layer region between the stream and theassociated wall. This tends to further reduce the pressure in this areaand thus increase the boundary layer effect and consequently the lock-oneffect on the stream. However, as the passage becomes backloaded due tothe mattress passages becoming nearly fully inflated, the staticpressure in the output passage begins to build up and is transmittedthrough the feedback channel to the control nozzle rapidly increasingthe pressure in a boundary layer region and assisting in a rapidbreaking of the boundary layer effect. Therefore, switching of the powerstream may be effected at a relatively precise pressure due tobackloading of the stream. Specifically, rate of flow of fluid adjacentthe sidewall remains relatively constant, maintaining a relativelyconstant differential in pressure across the power stream. It followsthat a specific pressure and consequent flow must be applied to thecontrol nozzle to switch the power stream. This specific pressure can beobtained only after the mattress passages have achieved a predetermineddegree of inflation and thus controlled switching is obtained.

It is an object of the present invention to provide a pure fluidflip-flop for alternately and cyclically inflating alternately arrangedair cells in a mattress or the like which flip-flop when connected tothe mattress operates as a low speed oscillator.

It is another object of the present invention to provide a pure fluidcontrol for mattresses or similar body support devices havingalternately arranged inflatable passages which flip-flop device isinexpensive to manufacture and trouble-free in operation.

It is another object of the present invention to employ a pure fluidflip-flop with a mattress or similar body support having alternatelyarranged isolated inflatable air passages which flip-flop when connectedto the mattress operates as an oscillator having a highly reliable andstable cycle of operation.

The above and still further objects, features and advantages of thepresent invention will become apparent upon consideration of thefollowing detailed description of one specific embodiment thereof,especially when taken in conjunction with the accompanying drawings,wherein:

FIGURE 1 is a diagrammatic illustration of a bistable flip-flop withfeedback which may be employed to drive the mattress of the presentinvention;

FIGURE 2 is a diagrammatic illustration of the apparatus .of FIGURE 1connected to an inflatable mattress; and

FIGURE 3 is a schematic view of the mattress of FIG- URE 2 in elevationshowing alternately arranged inflated and deflated portions.

Referring now specifically to FIGURE 1, there is illustrated a purefluid flip-flop generally designated by the reference numeral 1 whichmay be employed in accordance with the present invention to operate amattress having alternately arranged groups of inflatable air passagesadapted to be inflated out-of-phase with one another.

The flip-flop comprises a power nozzle 2 for directing fluid through aninteraction region 3 towards two output passages 4 and 6. Theinteraction region is defined along its left and right sides bysidewalls 7 and 8. The sidewalls are positioned relative to thecenterline of the nozzle 2 such that, when a stream is deflected to oneof the .output passages, a low pressure boundary layer reigon isdeveloped between the stream and one of the sidewalls to maintain thestream locked to the adjacent sidewall.

More particularly, if the stream issued by the nozzle 2 is initiallydeflected, for instance, to the passage 4, it will be noted that thestream passes relatively close to the wall 7. The rapidly moving streamtends to evacuate, entrain, the fluid existing between the stream andthe sidewall 7 at a far more rapid rate than it can evacuate the fluidfrom the remainder of the interaction region 3 which is, under thesecircumstances, quite large relative to the region existing between thestream and the sidewall 8. Thus, the pressure in the region between thestream and the sidewall 7 is considerably less than the pressure in theremainder .of the interaction region. This differential in pressuremaintains the stream directed towards the output passage 4.

As previously indicated, the flip-flops are of two types: those whichswitch due to backloading and those which do not switch, even thoughfully backloaded. The flip-flop 1 .of FIGURE 1 is of the type which doesnot switch due to backloading and, more particularly, is known as aflip-flop having memory. The ability of the stream to remain switched tothe passage 4 in spite of backloading results from several factors suchas the length of the interaction region 3, the placement of sidewalls 7and 8 and other factors now to be discussed. The outlet passages 4 and 6are defined in part by extensions of sidewalls 7 and 8 and by a divider9, which in this particular instance, is symmetrical with the centerlineof the nozzle 2. The distance of the downstream end 11 of the divider 9from the egress orifice of the nozzle 2 is one factor in determining theability of the device to remain locked to a wall in the presence ofload. A cusp 18 formed at the upstream end of divider 9 creates a vortexflow in such a direction that the flow in the vertex is directed againstthe side of the stream remote from the sidewall to which the stream isattached and thus, further enhances the differential pressure across thestream.

In addition, a small booster region 12 is provided between the egressorifice of the nozzle 2 and control passages .13 and 14 to be discussedsubsequently. The sidewalls of the booster region 12 are close to thepower stream and a boundary layer effect is established between thepower stream and the sidewall of the booster region along the side ofthe device to which the stream is deflected. This region issubstantially completely isolated from the output passages 4 and 6 andthe loads thereon and therefore tends to maintain the stream in theposition directed regardless of load.

The device is also provided with a pair of vents 16 and 17, the purposeof which is to vent excess fluid provided to a passage after the passageis blocked. If, for instance, the stream is directed to passage 4 andthe passage can accept no more fluid due to blockage, the power streambeing locked to sidewall 7 continues to deliver fluid to the passage. Aflow path must be supplied for this excess fluid and in the absence ofthe vent 17, the fluid would be directed to output passage 6,pressurizing this latter passage, an undesirable effect. The vents 16and 17 provide passages for the excess fluid and thus permit the passage6 to remain at a low pressure.

As stressed above, the flip-flop of FIGURE 1 is a memory type unit whichwill not switch on backload and in order to effect switching, theapparatus is provided with a pair of feedback channels 19 and 21. Thechannels 19 and 21 operate under one condition of flow as positivefeedback channels and under another set of conditions operate asnegative feedback channels. Specifically, when the stream is initiallydirected to the channel 4, the rapid movement of air past the upper endof the passage 19 which, for purposes of explanation, is designated bythe reference numeral 22, extracts air from the passage and thuswithdraws further fluid from the boundary layer region through thecontrol nozzle .13. In order to accomplish this result, the passage 19preferably enters the output channel 4 at an angle of betwen 0-90. At agreater angle, some of the fluid flowing through the output channeltends to enter passage 19 and defeat the positive feedback effect. Thus,upon initial deflection of the stream, the feedback channel 19 operatesas a positive feedback channel be cause it enhances the boundary layereffect. Upon the passage 4 becoming sufliciently backloaded tosubstantially raise the pressure in this passage, the flow past theopening 22 is stopped so that fluid can no longer be extracted from thepassage 19. In addition, the increase of pressure in the channel 4 istransmitted through the feedback passage 19 and the nozzle 13 into theboundary layer region between the stream and the sidewall. By thisprocess, the pressure in this region is raised above the pressure in theremainder of the interaction region 3 and the stream is caused to switchto the passage 6.

The device is completely symmetrical and therefore the cycle repeatsitself. Thus, if the passages 4 and 6 are equally and alternatelybackloaded, a symmetrical cycle of operation is effected and the deviceswitches any rate determined by the fluid capacity of the load and thepower stream pressure and flow rate. If the passages 4 and 6 wereblocked at the ends where they are ended in FIGURE 1, the switching ratewould be quite great. However, if the capacity of the load is quitelarge, then the switching rate is low. Regardless of the load, however,switching occurs at a precise pressure in the output passages 4 and 6due to the use of the memory type unit with the feedback passages 19 and21. More particularly, the flow past the sidewall lock-on region asdesignated by reference numerals 7 and 8, due to the presence of thevent passages 16 and 17, remains at a relatively high rate and isrelatively independent of the size of the load. Thus, the reducedboundary layer pressure is relatively constant and switching must dependupon the pressure in the output passages achieving a specific value suchthat suflicient fluid issues through the control nozzles 13 and 14 tobreak the boundary layer effect.

Referring now specifically to FIGURES 2 and 3 of the accompanyingdrawings, there is illustrated the pure fluid flip-flop 1 connected to amattress generally designated by the reference numeral 23 with which theflip-flop is to be employed. The mattress comprises a first plurality ofinflatable passages 24 arranged in alternating relationship with asecond plurality of inflatable air passages 26. The passages 24 areconnected through a manifold 27 to output passage 6 of the flip-flop 1while the passages 26 are connected via a manifold 28 to the outputpassage 4 of the flip-flop 1.

In operation, the power nozzle 2 is connected to a source of airpressure and, for instance, fluid is initially directed to the passage4. As seen in FIGURE 3, the flow to the passage 4 produces inflation ofthe interconnected air passages 26 while the pressure in the passages 24which are arranged in alternation with the passage 26 is greatly reducedand these elements become substantially flat. In consequence, the weightof the body of the user is supported on the upper layer of materialdefining the passages 26. After the passage 26 becomes substantiallyfully inflated, back pressure in the passage 4 increases and producesswitching via the feedback channel 19.

Air pressure is now supplied through the manifold 27 to the passages 24and these passages assume the shape of the passage 26 as illustrated inFIGURE 3 while the passages 26 are deflated and assume the illustratedshape of the passages 24. Thus, the body of the user is now supported onthe upper surface of the material defining passages 24 and the areas ofprior contact between the material defining passage 26 and the body isnow under considerably lesser pressure which is a desirable feature inthe elimination of bed sores.

Referring again to FIGURE 2, it will be noted that the feedback lines 19and 21 have restrictions 27 and 28 formed therein. These restrictionsare necessitated by the gain of the unit. Specifically, a flip-flop haspressure gain. The mattress 23 must support a person and as such, apressure of, for instance, 1 to 2 p.s.i.g. must be supplied to themattress and thus appears in passages 4 and 6. Due to gain of theflip-flop, pressures of only 0.1 to 0.2 p.s.i.g. are required to switcha power stream capable of producing pressures of 1 to 2 p.s.i.g. in themattress. Thus, the restrictions 27 and 28 are required to drop thepressure at the control nozzles 13 and 14 to the proper value.

The cycle of operation is preferably slow, occurring everytwo-and-a-half-to-three minutes. As indicated above, the frequency isdetermined by the size of the nozzle 2 and therefore a unit may bedesigned for any desired frequency within reason, of course.

An important feature of the present invention is the ability of theapparatus to be employed where there is no electricity available or itis not desired to operate the apparatus from an electrical supply. Moreparticularly, the flip-flop 1 connected to the mattress may be operatedfrom a compressed air source such as bottled compressed air or thecompressed air supplies in hospital rooms which supplies are found inthe more modern hospitals. Thus, the motor and pump may be eliminatedand, in consequence, the element 1 may be attached directly to themattress and form a composite part therewith.

The apparatus is not necessarily limited to utilization with mattresses.It may be employed for pads in automobiles, particularly in trucks wherea ready supply of compressed air is available from the air-brakecompressor. The apparatus may also be employed in automobiles byproviding a small pump motor driven from the 12-volt supply found in thestandard automobile today. Thus, the apparatus is completely portableand, in many instances is completely independent of electricity wherecompressed air supplies are available. As previously indicated, thefluid flip-flop is quite light, relatively simple to manufacture. Atypical fluid flip-flop may be less than two inches along each side andless than one inch thick, its weight amounting to less than a pound.

While I have described and illustrated one specific embodiment of myinvention, it will be clear that variations of the details ofconstruction which are specifically illustrated and described may beresorted to without departing from the true spirit and scope of theinvention as defined in the appended claims.

What I claim is:

1. An inflatable mattress or the like and control therefor comprising amattress having at least a first group and a second group of inflatableregions, the inflatable regions of said first group of inflatableregions being generally interleaved with and isolated from theinflatable regions of said second group of inflatable regions, a firstfluid flow means connected to supply fluid to said first group ofinflatable regions, a second fluid flow means connected to supply fluidto said second group of inflatable regions, a pure fluid bistableelement having an interaction region, at least a first output passageand a second output passage, a power nozzle for issuing a power streamof fluid through said interaction region toward said output passages,means connecting said first and second output passages to said first andsecond fluid flow means, respectively, first means responsive toinflation of said first group of inflatable regions for switching thepower stream from said first output passage to said second outputpassage, and means responsive to inflation of said second group ofinflatable regions for switching the power stream from said secondoutput passage to said first output passage.

2. An inflatable member and control therefor comprising an inflatablemember having at least two inflatable regions isolated from one another,a firs-t fluid flow means connected in fluid flow relationship to afirst of said inflatable region, a second fluid flow means connected influid flow relationship to a second of said inflatable regions, a purefluid bistable element having an interaction region, at least a firstoutput passage and a second output passage, a power nozzle for issuing apower stream of fluid through said interaction region toward said outputpassages, means connecting said first and second output passages to saidfirst and second fluid flow means, respectively, first control meansresponsive to inflation of said first inflatable region for switchingthe power stream from said first output passage to said second outputpassage and second control means responsive to inflation of said secondinflatable region to switch said power stream from said second outputpassage to said first output passage.

3. The combination according to claim 2 wherein said first control meanscomprises a first feedback means responsive to pressure in said firstoutput passage for issuing fluid into said interaction region in such asense as to deflect said power stream from said first output passage tosaid second output passage.

4. The combination according to claim 3 wherein said second controlmeans comprises a second feedback means responsive to pressure in saidsecond output passage for issuing fluid into said interaction region insuch a sense as to deflect said power stream from said second outputpassage to said first output passage.

5. The combination according to claim 4 wherein said flip-flop includesa first control nozzle disposed on the same side of the centerline ofsaid power nozzle as said first output passage, and a second controlnozzle disposed on the same side of the centerline of said power nozzleas said second output passage, said first feedback means extendingbetween said first output passage and said first control nozzle and saidsecond feedback means extending between said second output passage andsaid second control nozzle.

6. The combination according to claim 5 wherein said sages at an anglesuch that movement of the power stream through one of said outputpassages extracts fluid from its associated feedback means.

7. The combination according to claim 4 wherein said pure fluid bistableelement is of the type in which switching is insensitive to backloadingof said output passages in the absence of said first and second feedbackmeans.

References Cited UNITED STATES PATENTS 2,460,245 1/1949 Summerville12833 2,684,672 7/1954- Summerville 128-33 3,098,504 7/1963 Joesting137-624.14

feedback means enter into their respective output pas- 1 L TRAP? PrimaryExaminer

